Instead, he uses his smartphone to split restaurant checks and pay rent, using eBay’s mobile payment tool called Venmo. Like many of his peers, he has taken to using the application’s name as a verb — telling friends to ‘‘Venmo me’’ — the way predecessors turned ‘‘Google’’ and ‘‘tweet’’ into action words.

Millennials, people born from the early 1980s to the early 2000s, have been flocking to these technologies, drawn by their ease of use and social features. Venmo, based in New York, alone handled $314 million in mobile payments in the first quarter of this year, up 62 percent from the prior quarter. Another tool gaining in popularity is Fiserv’s Popmoney.

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After downloading a mobile payment app onto a smartphone, users can connect them to bank and credit card accounts, and then link up with friends to send and receive money on the go.

The broader mobile wallet market, which in recent years drew entrants such as Google, initially was slow to catch on with a wide audience. The rising use of peer-to-peer applications among twentysomethings is improving the prospects for adoption of all kinds of smartphone-based payments.

‘‘I couldn’t have predicted then just how much it would infiltrate my financial life as it has, but now I live and die by it,’’ said Karuri, who uses the application to pay peers for everything from rent to drinks.

‘‘Especially in New York, you’re mostly going out with lots of friends, and there’s a lot of splitting bills — Venmo has taken over that game.’’

Online and mobile peer-to-peer transfers can be used anytime when people previously might have written a check or handed out cash, such as for rent, utilities, or bills for dining out.

About half of peer-to-peer payment users use the apps to split restaurant checks, according to a July Nielsen report. Gifts and entertainment, such as paying each other for concert tickets, are also popular.

Individuals exchange about $1 trillion in the United States every year, said Ron Shevlin, a senior analyst at Aite Group, a research and advisory firm. While mobile and electronic peer-to-peer applications won’t be able to capture the entire market, they have made gains and will ‘‘make a dent,’’ he predicted.

Caitlin Wood, 22, a recent college graduate in Raleigh, N.C., started using Venmo in February when she didn’t have cash to pay for her share of a burrito and margarita dinner. Her friend picked up the tab and told Wood to ‘‘Venmo’’ her. Since then, she’s been using it about once a week for everything from paying utilities to splitting meal checks.

The apps are free to download, and most levy modest fees for transactions. Some charge for sending money through a credit or debit card. Others might charge for sending, though not for receiving.

Dwolla, a P2P payment network startup, takes 25 cents from those receiving more than $10, while Venmo users who send money through a credit card get docked 3 percent.

Millennials already spend $1.3 trillion as consumers annually, according to a January report by Boston Consulting Group. They are also already the biggest users of all mobile payment apps, with 18- to 34-year-olds accounting for about 55 percent of those who use the digital services, Nielsen found.

‘‘The early adopters grew up with mobile social media,’’ said Bill Ready, chief executive of Venmo and Braintree Payment Solutions.

The increasing interest in P2P has spurred payments companies and financial institutions to roll out apps through acquisitions and partnerships. Braintree, itself acquired by eBay for $800 million last year, bought Venmo in 2012 for $26.2 million to break into the P2P payments space.

Startup Square purchased P2P payments application Evenly for an undisclosed price in December 2013 — months after rolling out its own person-to-person service, Square Cash.

The services are growing rapidly. The total volume of mobile and online P2P payments through financial institutions and nonbank providers such as PayPal — also owned by eBay — reached $74.9 billion in 2013 and is projected to increase significantly, according to Javelin Strategy & Research.

In April, eBay chief executive John Donahoe cited Venmo’s ‘‘explosive growth on college campuses’’ in the P2P business and said that while it has no revenue, the app serves as a way to extend the reach of PayPal, which pioneered online peer-to-peer payments more than 15 years ago, and shows the ‘‘power of mobile payments.’’

No single provider dominates the market so far, as companies take on different roles in the space. Some are used for larger transactions such as bill payments, while others promote their services for smaller transfers, said Aleia Van Dyke, a payments analyst at Javelin.

Baldwin Giang, 22, a recent graduate who just moved to New York, was the last one in his group of friends who didn’t have Venmo because he was nervous about giving his banking information to an online application.

‘‘I was at some restaurant with my friends and I was basically peer-pressured to get Venmo,’’ he said. ‘‘I didn’t have cash on me and they were like, ‘You’re being a barbarian, you just need to get it.’ ”

Financial institutions that do not offer P2P services, such as through partnerships with app providers, risk losing younger customers, according to Javelin.

‘‘They like the social aspect of the communication, and it also serves as a reminder to an individual of who hasn’t paid,’’ said Ron Mazursky, director of the debit advisory service at Mercator Advisory Group, which provides analysis for the payments and banking industries.

The power of community also helps explain increased millennial use of person-to-person payment services. College campuses, in particular, foster viral adoption of new technologies, said Kamran Ansari, an investor at Greycroft Partners who invested in both Venmo and Braintree.

Student Justin Schuster, 21, was converted to Venmo not of his own volition recently during a brunch with three friends. One of them wanted to put the entire check on his credit card for rewards points, and insisted that everyone else pay their share through Venmo. ‘‘This was the first time I’d ever had an incentive or need to use it,’’ he said. ‘‘I ended up using it two more times in the same day.’’

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